SV-270716r1066637: Ubuntu 24.04 LTS default filesystem permissions must be defined in such a way that all authenticated users can read and modify only their own files. | Canonical Ubuntu 24.04 LTS STIG SCAP Benchmark

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Assessment Title

Rule Text

Ubuntu 24.04 LTS default filesystem permissions must be defined in such a way that all authenticated users can read and modify only their own files.

Description

Discussion Text

Setting the most restrictive default permissions ensures that when new accounts are created, they do not have unnecessary access.

How this relates to the STIG checklist: STIG vs SCAP benchmark.

IA Controls

NIST SP 800-53

Not mappedCCI-000366

References

DPMS Target Canonical Ubuntu 24.04 LTS DISA DPMS Target Canonical Ubuntu 24.04 LTS 5673

SCC Automation Reference

The reconstructed evaluation script behind this rule's OVAL check(s) — every module a compound check combines, with this rule's own concrete values and DISA's SCC tool's real per-module mechanism curated from static teardown of SCC releases.

#!/bin/bash
# Reconstructed from oval:mil.disa.stig.ubuntu2404os:def:270716
# Ubuntu 24.04 LTS default filesystem permissions must be defined in such a way that all authenticated users can read and modify only their own files.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# /etc/login.defs:UMASK == 077
# textfilecontent54_object (textfilecontent54_test)
test_1() {
  (sed -En 's/^\s*UMASK\s+([^#\s]+)/\1/p' '/etc/login.defs') | grep -qxF '077'
}

if test_1; then
  echo "PASS"
else
  echo "FAIL"
fi

Assessment Script Powered by AISandbox-executed

A standalone Shell script to assess this control automatically. Review before running it in your environment.

Syntax-checked and actually executed in an isolated sandbox (not the real system this checks) — confirmed to run without errors.

#!/bin/sh
# OVAL Definition: oval:mil.disa.stig.ubuntu2404os:def:270716
if [ ! -f "/etc/login.defs" ]; then echo "PASS"; exit 0; fi
if grep -q "^\\s*UMASK\\s+077" /etc/login.defs; then echo "PASS"; exit 0; else echo "FAIL"; exit 1; fi

Remediation

Configure the system to define the default permissions for all authenticated users in such a way that the user can read and modify only their own files. 
 
Edit the "UMASK" parameter in the "/etc/login.defs" file to match the example below: 
 
UMASK 077